Some background to this invention is shown in the following references:
1. Jaffe', M.: Ueber den Niederschlag welchen Pikrinsaeure in normalen Harn erzeugt und ueber eine neue Reaction des Kreatinins. Z. Physiol. Chem. 10, 391-400 (1886).
2. Tanganelli, E., Prencipe, L., Bassi, D., Cambiaghi, S. and Murador, E.: Enzymic assay of creatinine in serum and urine with iminohydrolase and glutamate dehydrogenase. Clin. Chem. 28, 1461-1464 (1982).
3. Soldin, S.J. and Hill, G.J.: Micromethod for determination of creatinine in biological fluids by high-performance liquid chromatography combined with a continuous-flow microanalyzer. Clin. Chem. 24, 747-750 (1978).
4. Blass, K.G.: Polarographic studies of the reactivity of bilirubin ditaurine conjugate with alkaline picrate. Microchem. J. 35, 334-339 (1987).
5. Blass, K.G. and Ng, D.S.K.: Reactivity of acetoacetate with alkaline picrate: An interference of the Jaffe' reaction. Clin. Biochem. 21, 39-47 (1988).
6. Viraraghavan, S. and Blass, K.G.: Effect of glucose upon alkaline picrate: A Jaffe' interference. J. Clin. Chem. Clin. Biochem. 28, 95-105 (1990).
7. Benedict, S.R. and Behre, J.A.: Some application of a new color reaction for creatinine. J. Biol. Chem. 114, 512-532 (1936).
8. Bolliger, A.: the colorimetric determination of creatinine in urine and blood with 3,5-dinitrobenzoic acid. Med. J. Austr. 2, 818-821 (1936).
9. Langley, W.D. and Evans M.: The determination of creatinine with sodium 3,5-dinitrobenzoate. J. Biol. Chem. 115, 333-341 (1936).
10. Parekh, A.C., Cook, S., Sims, C., and Jung, D.H.: A new method for the determination of serum creatinine based on reaction with 3,5-dinitrobenoyl chloride in an organic medium. Clin. Chim. Acta 73, 221-231 (1976).
11. Sims, C. and Parekh, A.C.: Determination of serum creatinine by reaction with methyl-3,5-dinitrobenzoate in methyl sulfoxide. Ann. clin. Biochem. 14, 227-232 (1977).
12. Blass, K.G., Thibert, R.J. and Lam, L.K,: A study of the mechanism of the Jaffe' reaction. Z. Klin. Chem. Klin. Biochem. 12, 336-343 (1974).
13. Ng, D.S.K. and Blass, K.G.: Reactivity of Hydroxide ion with picrate as related to the Jaffe' reaction. Microchem. J. 36, 89-97 (1987).
Laboratory methods employed for the determination of creatinine in body fluids may be summarized as procedures based upon the Jaffe' reaction (1), coupled enzymatic reactions (2), and high-performance liquid chromatography (HPLC) (3). These methods have varying degrees of specificity (4-6) with the simplest economical procedures being based upon the alkaline picrate Jaffe' reaction which was first published in 1886. Dependent upon the modifications introduced, specificity has been improved, however no routine modified Jaffe' method is free of interference. More costly coupled enzymatic methods have been developed, however these are not in widespread use. While HPLC methods are highly specific and even being considered as reference methods, they are not practical for routine high-volume testing purposes.
The reactivity of creatinine with alkaline 3,5-dinitrobenzoate to produce a purple colored product was first described in the literature in 1936 (7-9). The colorimetric reaction has subsequently been praised for its specificity, but also criticized for its lack of sensitivity. Further improvements have been claimed by employing 3,5-dinitrobenzoyl chloride (10) or methyl-3,5-dinitrobenzoate (11) as reagents for the colorimetric determination of creatinine.